Is this normal behaviour?
Yes. Note, this is not a Perl issue. The only way environment variables are "shared" is that when a process forks, both parent and child get identical copies. And on an exec, the environment persists.
How can I permanently set PERL5LIB?
Set it in the process that spawns the xterms. Or by setting it in the shell profile that's run each time an xterm starts.

In reply to Re: PERL5LIB resets in a new terminal window by JavaFan
in thread PERL5LIB resets in a new terminal window by colicab

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